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City of Pleasanton 4.0 Water Agency Background Final Water Supply Assessment Stoneridge Drive Specific Plan Amendment and Staples Ranch Project Table 5-1: Average Annual Precipitation, Evapotranspiration and Irrigation Demands Month ETo in a Average Total Preci station in b Irrl ation Demand in Janua 0.82 2.91 0.0 Februa 1.47 2.57 0.0 March 2.92 2.12 0.9 A ril 4.4 1.12 3.8 Ma 5.57 0.44 6.0 June 6.66 0.1 7.7 Jul 7.4 0.02 8.6 Au ust 6.35 0.05 7.4 Se tember 4.73 0.16 5.3 October 3.34 0.7 3.1 November 1.54 1.72 0.0 December 1.01 2.63 0.0 Annual 46.21 14.54 42.8 3.58 ac-ft/acre Notes: a. CIMIS -Station 191. b. Western Regional Climate Center. c. 5 ercent leachin fraction and 90 ercent distribution uniforms 5.3.2 Supply Sources Zone 7 has three main sources of water: State Water Project (SWP) water via the South Bay Aqueduct (SBA), surface runoff collected in the Lake Del Valle Reservoir, and groundwater. SWP surface water makes up the bulk of the regional water supplies conveyed by Zone 7 to its retail customers. These sources combined supply nearly all of the water to the cities of Dublin, Livermore, and Pleasanton. e 5.3.3 Zone 7 Water Supplies Zone 7's three main sources of water supply are divided into five subcategories: 1) the Livermore- Amador Valley Groundwater Basin; 2) Out-of-Basin water storage options); 3) contracted SWP supplies; 4) water through Lake Del Valle system; and 5) recycled water. The following discussions present the planned and existing uses of each category. 5.3.4 Local Groundwater 5.3.4.1. The Livermore-Amador Valley Groundwater Basin The Livermore-Amador Valley Groundwater Basin (LAVGB) is in the heart of the Livermore Valley, extends south into the hills south of Pleasanton and Livermore. Figure 6 presents groundwater basin information and well locations. It includes 65,000 acres occupied by both the Livermore Valley (42,000 acres) and the Livermore Uplands (23,000 acres). A major portion of the LAVGB is the Main Groundwater Basin (Main Basin), which covers an area of over 17,000 acres and has the highest-yielding aquifers and best quality water.9 The DWR Bulletin 118 has not identified the Main Basin (DWR Basin No. 2-10) in an overdraft condition or a basin expected to be in overdraft in the The municipal retailers supplement their Zone 7 supplies by pumping their GPQ from the Main Basin; the safe yield from natural recharge of the Main Basin is calculated at 13,400 AFA. Zone 7 Water Agency Groundwater Management Plan, 2005, page 3-4. P:\Projecls - WP OnIy141162.01 Staples Ranch WSA\FinaOFine1 WSA.doc 5~